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Mohammad Esmaeili Safa

Bio: Mohammad Esmaeili Safa is an academic researcher from University of Mazandaran. The author has contributed to research in topics: Stress intensity factor & Crystallite. The author has an hindex of 3, co-authored 3 publications receiving 16 citations.

Papers
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Journal ArticleDOI
TL;DR: In this paper, the authors explored the mechanics of monocrystalline and polycrystalline (PC) silicon-germanium nanosheets (MSiGeNS and PSiGeNs, respectively) as a function of temperature.

19 citations

Journal ArticleDOI
TL;DR: In this article, the fracture fingerprint of polycrystalline SiC nanosheets (PSiCNSs) was analyzed using molecular dynamics simulation (MDS) and the results showed that the fracture strength of PSiCns decreased with temperature.

16 citations

Journal ArticleDOI
TL;DR: In this article, the number of grains with random configuration, temperature, and crack length were systematically changed to track the mode and the intensity of failure of model polycrystalline carbon nanosheets.
Abstract: Polycrystalline carbon nanosheets are composed of several randomly rotated monocrystalline regions facing each other in grain boundaries-the cause of stress concentration-that affects the mechanics of 2D carbon nanostructures. They have been widely used in different fields, particularly in electronic devices. Herein, heterogeneous graphitic carbon nitride (C3N) was considered as typical of polycrystalline carbon nanosheets for modelling its fracture behavior. The number of grains with random configuration, temperature, and crack length were systematically changed to track the mode and the intensity of failure of model nanosheets. Molecular dynamics simulations predictions unraveled the interatomic interaction in the C–C and C–N bonds. An increase in the number of grain boundaries from 3 to 25 as well as the length of crack led to more than 70% fall in the Young’s modulus of polycrystalline carbon platelets. Stress intensity factor decreased against temperature, but increased by crack length enlargement demonstrating higher fracture toughness of small cracks. This theoretical approach can be generalized to capture the unique fracture fingerprint of polycrystalline carbon structures of different types.

15 citations

Journal ArticleDOI
TL;DR: In this paper , the authors proposed a sustainable strategy and a technoeconomic analysis of off-grid hybrid energy systems (HES) in remote islands of Iran, including Lavan, Larak, and Failaka, utilizing PV module, wind turbine, and hydrokinetic turbines.
Abstract: Sustainable generation is impacted by the adoption of renewable energy, the growth of energy markets, and economic strategies. This paper offers a sustainable strategy and a technoeconomic analysis of off-grid hybrid energy systems (HES) in remote islands of Iran, including Lavan, Larak, and Failaka, utilizing PV module, wind turbine, and hydrokinetic turbines. Hourly wind speed, solar irradiation, and hydrovelocity have been implemented under load following (LF) and cycle charging (CC) dispatch strategies in order to ascertain the most appropriate systems. Lavan Island achieves the winning HES with a CC dispatch strategy, which consists of 3 hydroelectric turbines, 1 wind turbine, 349 kW of solar power, 150 kW of generator power, 316 kWh of batteries, and 287 kW of the converter. This ideal HES, which generates a consistent generation profile and reasonable net present cost (NPC) and cost of energy (COE) of M0.160$ and $0.013 kWh, respectively, can be practically attained in these areas. LF-controlled optimal solutions use less fuel than CC-based ones, leading to a higher share of renewable energy. Compared to Larak and Lavan, the CC- and LF-controlled options on Failaka Island generate cleaner electricity with emissions that are 57% and 44% lower. Regarding the ability to recoup the project’s initial investment costs, long-term energy production would be more financially viable than short-term. Short-term projects with higher financial uncertainty due to the salvage cost should use the CC method.

2 citations


Cited by
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01 May 1993
TL;DR: Comparing the results to the fastest reported vectorized Cray Y-MP and C90 algorithm shows that the current generation of parallel machines is competitive with conventional vector supercomputers even for small problems.
Abstract: Three parallel algorithms for classical molecular dynamics are presented. The first assigns each processor a fixed subset of atoms; the second assigns each a fixed subset of inter-atomic forces to compute; the third assigns each a fixed spatial region. The algorithms are suitable for molecular dynamics models which can be difficult to parallelize efficiently—those with short-range forces where the neighbors of each atom change rapidly. They can be implemented on any distributed-memory parallel machine which allows for message-passing of data between independently executing processors. The algorithms are tested on a standard Lennard-Jones benchmark problem for system sizes ranging from 500 to 100,000,000 atoms on several parallel supercomputers--the nCUBE 2, Intel iPSC/860 and Paragon, and Cray T3D. Comparing the results to the fastest reported vectorized Cray Y-MP and C90 algorithm shows that the current generation of parallel machines is competitive with conventional vector supercomputers even for small problems. For large problems, the spatial algorithm achieves parallel efficiencies of 90% and a 1840-node Intel Paragon performs up to 165 faster than a single Cray C9O processor. Trade-offs between the three algorithms and guidelines for adapting them to more complex molecular dynamics simulations are also discussed.

29,323 citations

Journal ArticleDOI
TL;DR: In this paper, the authors explored the mechanics of monocrystalline and polycrystalline (PC) silicon-germanium nanosheets (MSiGeNS and PSiGeNs, respectively) as a function of temperature.

19 citations

Journal ArticleDOI
TL;DR: In this article, the fracture fingerprint of polycrystalline SiC nanosheets (PSiCNSs) was analyzed using molecular dynamics simulation (MDS) and the results showed that the fracture strength of PSiCns decreased with temperature.

16 citations

Journal ArticleDOI
TL;DR: In this article, a series of polycrystalline Boron carbide nanosheets (PCBC3NSs) were evaluated for thermal conductivity varying the number of grains (3, 5, and 10), and the effect of grain rotation was also modeled in terms of Kapitza thermal resistance per grain.
Abstract: Boron carbide nanosheets (BC3NSs) are semiconductors possessing non-zero bandgap. Nevertheless, there is no estimation of their thermal conductivity for practical circumstances, mainly because of difficulties in simulation of random polycrystalline structures. In the real physics world, BC3NS with perfect monocrystalline is rare, for the nature produces structures with disordered grain regions. Therefore, it is of crucial importance to capture a more realistic picture of thermal conductivity of these nanosheets. Polycrystalline BC3NS (PCBC3NSs are herein simulated by Molecular Dynamics simulation to take their thermal conductivity fingerprint applying ΔT of 40 K. A series of PCBC3NSs were evaluated for thermal conductivity varying the number of grains (3, 5, and 10). The effect of grain rotation was also modeled in terms of Kapitza thermal resistance per grain, varying the rotation angle ( θ /2 = 14.5, 16, 19, and 25°). Overall, a non-linear temperature variation was observed for PCBC3NS, particularly by increasing grain number, possibly because of more phonon scattering (shorter phonon relaxation time) arising from more structural defects. By contrast, the heat current passing across the slab decreased. The thermal conductivity of nanosheet dwindled from 149 W m−1 K−1 for monocrystalline BC3NS to the values of 129.67, 121.32, 115.04, and 102.78 W m−1 K−1 for PCBC3NSs having 2, 3, 5, and 10 grains, respectively. The increase of the grains rotation angle (randomness) from 14.5° to 16°, 19° and 25° led to a rise in Kapitza thermal resistance from 2⨯10−10 m2 K·W−1 to the values of 2.3⨯ 10−10, 2.9⨯10−10, and 4.7⨯ 10−10 m2 K·W−1, respectively. Thus, natural 2D structure would facilitate phonon scattering rate at the grain boundaries, which limits heat transfer across polycrystalline nanosheets.

15 citations

Journal ArticleDOI
TL;DR: In this article, the effect of grain boundaries of heptagon-pentagon defect pairs on thermal properties of BC3GrHs with various defects were evaluated using molecular dynamic simulations.
Abstract: Simulation of thermal properties of graphene hetero-nanosheets is a key step in understanding their performance in nano-electronics where thermal loads and shocks are highly likely. Herein we combine graphene and boron-carbide nanosheets (BC3N) heterogeneous structures to obtain BC3N-graphene hetero-nanosheet (BC3GrHs) as a model semiconductor with tunable properties. Poor thermal properties of such heterostructures would curb their long-term practice. BC3GrHs may be imperfect with grain boundaries comprising non-hexagonal rings, heptagons, and pentagons as topological defects. Therefore, a realistic picture of the thermal properties of BC3GrHs necessitates consideration of grain boundaries of heptagon-pentagon defect pairs. Herein thermal properties of BC3GrHs with various defects were evaluated applying molecular dynamic (MD) simulation. First, temperature profiles along BC3GrHs interface with symmetric and asymmetric pentagon-heptagon pairs at 300 K, ΔT = 40 K, and zero strain were compared. Next, the effect of temperature, strain, and temperature gradient (ΔT) on Kaptiza resistance (interfacial thermal resistance at the grain boundary) was visualized. It was found that Kapitza resistance increases upon an increase of defect density in the grain boundary. Besides, among symmetric grain boundaries, 5-7-6-6 and 5-7-5-7 defect pairs showed the lowest (2 × 10-10 m2 K W-1) and highest (4.9 × 10-10 m2 K W-1) values of Kapitza resistance, respectively. Regarding parameters affecting Kapitza resistance, increased temperature and strain caused the rise and drop in Kaptiza thermal resistance, respectively. However, lengthier nanosheets had lower Kapitza thermal resistance. Moreover, changes in temperature gradient had a negligible effect on the Kapitza resistance.

13 citations